The invention relates to railroad car trucks or bogies. More particularly, the invention is in relation to a railroad car truck which is manufactured and sold by National Castings Incorporated of Lisle, Ill. under the trademark SWING MOTION. A detailed description of this quality, heavy duty truck with excellent high speed performance characteristics is found in U.S. Pat. No. 3,670,660 which is made a part hereof.
The SWING MOTION truck is manufactured from many different steel parts, such as a bolster and transom which are coupled transversely between a pair of parallel sideframes between which a pair of axles with attached wheels are mounted for rotation. The transom is generally parallel to the bolster, but in closer spaced relation to the railroad trackway, when the truck is mounted on the trackway. The transom has a pair of opposing ends which are mounted, e.g. bolted, on similar rocker seats, each of which seats comprises a rectangular plate with a semi-cylindrical projection or head that extends from the plate towards the trackway and rests in supported relation on a pair of coaxially spaced, hardened, U-shaped rocker seat bearings which are restricted for movement in open, slightly larger, rectangular channels that are formed in the sideframes below the connection of the bolster ends with the sideframes.
The current configuration of the SWING MOTION truck, including the present, bolted transom and bearing arrangement, has demonstrated a high degree of performance in terms of high speed stability and low maintenance costs. Recent tests for inter-axle shear stiffness (lASS) have shown that this bolted transom arrangement contributes significantly to the lASS, which is a major factor in high speed stability and improved wheel wear.
Further improvement in lASS can be achieved through the invention which is in a different rocker seat and bearing assembly which solves shortcomings of the current arrangement relating to, I) potential wear or lock up of the arrangement in adverse, particularly sandy environments, and II) the problems of maintaining the proper clearance between the transom, rocker seat, and sideframe.
Briefly stated, the invention is in a rocker seat which includes at least one inwardly directed, recess which is at least parti-cylindrical, in shape, and which is transversely disposed to the longitudinal axis of the transom. Each recess is designed to receive a matingly curved head which protrudes from an adjacent, vertically aligned, hardened steel bearing which is disposed in stationary relation within a slightly larger channel that is formed in the adjacent sideframe. The at least parti-cylindrical heads of the bearings are generated by a radius which is slightly smaller than the radius used in the formation of the at least parti-cylindrical recesses in the rocker seats, to facilitate relative rocking motion between the sideframes and the rocker seats and attached transom which can be replaced by a plurality of tie rods without detracting from the invention.